Unwrap Mutex from broken_link_callback #1094

Job	Run time
lockfile	59s
build_wasm (nightly)	46s
build_lib_test (nightly)	51s
build_bin_spec (nightly)	1m 6s
build_wasm (beta)	4m 25s
build_lib_test (beta)	1m 19s
build_wasm (stable)	46s
build_bin_spec (beta)	1m 6s
no_features_build_test (nightly)	35s
build_lib_test (stable)	1m 1s
no_features_build_test (beta)	33s
build_bin_spec (stable)	1m 0s
build_lib_test ($MSRV)	2m 57s
no_features_build_test (stable)	40s
build_bin_spec ($MSRV)	3m 2s
build_wasm ($MSRV)	2m 30s
no_features_build_test ($MSRV)	2m 13s
clippy_format	2m 12s
	28m 1s

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